Engine management system - MEMS (Diagnostic connector): Description and operation

Diagnostic connector

A diagnostic connector, located on the passenger compartment fusebox, allows engine tuning or fault diagnosis to be carried out using TestBook without disconnecting the ECM harness multiplug.

Heated oxygen sensor

The engine management system operates a closed loop emission system to ensure the most efficient level of exhaust gas conversion.

A heated oxygen sensor, fitted in the exhaust down pipe, monitors the oxygen content of exhaust gases. The sensor generates a voltage related to the oxygen content of the exhaust. As the air/fuel mixture weakens, the exhaust oxygen content increases and so the voltage to the ECM decreases. If the mixture becomes richer, so the oxygen content decreases and the voltage increases.

From this signal the ECM can determine if the air/fuel mixture being delivered to the engine is rich or lean. The ECM can adjust the duration that the injectors are open to maintain the air/fuel ratio necessary for efficient gas conversion by the catalyst.

The heated oxygen sensor has an integral heating element to ensure an efficient operating temperature is quickly reached from cold. The electrical supply to the heater element is controlled by the ECM via the heated oxygen sensor relay in the relay module.